The invention relates to an electric heater with insulating carrying parts and heating conductors carried by the latter and with at least one tap for tapping a voltage lower than the voltage applied to the heating conductor, e.g. for a fan motor or the like.
The invention particularly relates to a heater in which the heating conductor between contact points with the carrying parts extends freely and spaced therefrom and within the area surrounded by the heating conductor the tap is fixed to the carrying part.
Taps on such heaters are used for tapping a voltage reduced compared with the mains voltage at the complete heater, e.g. for a fan motor or the like, which may only be supplied with a lower voltage. Heaters with such taps are in particular known from German Patent No. 2,722,213.
It is apparent from what has been stated hereinbefore that the precise tapping point of the tap on the heating conductor must be fixed for a specific operating member, such as a fan motor, but can differ in the case of different fan motors if they are to be supplied with different voltages. It frequently occurs that the further processor who has to fit such a heater in an electrical appliance, such as e.g. a warm air appliance or hair dryer, when using the same heater wishes to install different operational components, such as fan motors or changes occur to the motor over a period of time. The tapping point can also change as a function of the heating conductor wire used, because the voltage drop is dependent on the material and thickness. Moreover, for a given carrier, the winding manner can differ, in that different steepnesses are used for example leaving free individual wire reception notches or using more than one of wound wires.
Previously the taps were fixed to a particular point of the carrying part by using rivets or lugs. Admittedly, after winding the heating conductor, the tap could be lugfitted to the carrier. However, from the outset it was necessary to provide a punched hole for receiving the lug, so that the tap location was precisely predetermined. Complicated modifications were necessary on changing the point. It was not possible to keep stocks because, in the case of heaters with a fixed position of the tap, when it was necessary to change the position, the corresponding heaters would no longer be usable. has also been proposed to mount clamping tap elements on the edges of the carrying parts engaged round by the heating conductor turns. Such a construction is only possible with heaters constructed in a special radiator-like manner, in which additional carrying and insulting plates are provided outside the area given by the turns and to which the tap cables can be passed, fixed thereto and guided along the same. In addition, the meander-like guided heating conductors must have meander turns engaging over the carrying parts over a considerable length and with limited thickness, whereby said meander turns have a correspondingly large depth with limited spacing between the two legs. This can possibly lead to different problems, particularly the use of specific instead of random carrier types and materials. The taps can also only be fixed in snapping or clamping manner, i.e. not suitable for all uses and applications, although the known construction is highly suitable for certain purposes.
It is also known to provide on the outside of the casing of a heating conductor carrier in the form of a hollow cylinder, which outer casing carries radially arranged insulating plates and over whose outer edges are guided the heating conductor wire, grooves through sidewalls extending parallel from the cylinder casing and into which can be inserted a rail having teeth on its longitudinal sides, the downwardly bent flange of the rail being constructed as a tap. The rail is made from conductive material. Although this construction makes it possible to subsequently fix tap point, this is not in random form and is also complicated. Thus, to ensure that there is no projection over the heater, the rail end remote from the tap may have to be cut off. Moreover, the construction of the hollow cylinder and tap element is complicated and the latter involves considerable material expenditure. A construction including a groove is not even possible in the case of inexpensive planar heating conductor carriers made from clip material and the like.
Thus, the aim underlying the invention is to provide a heater which can be stocked and can be easily and inexpensively adapted in accordance with different operating parts, e.g. fan motors to be used therewith. According to the invention, in the case of an electric heater with insulating carrying parts and heating conductors carried by the latter and with at least one tap for tapping a voltage reduced compared with the voltage at the heating conductor, e.g. for a fan motor or the like, the carrying parts have slots through which pass the feet of a tap and through which the latter is fixed to the carrying part, with the length of the slots being greater than the width of the feet of the tap. As a result of the inventive construction it is possible for the tap to be moved along the slots within the carrying parts and consequently it is possible to modify the position of the tap relative to the turns and therefore the voltage drop along the turns. Thus, different voltages can be tapped on the heating conductor as a function of the tap position in the slot. Therefore the tapped voltage can be adapted to the operating part, such as a fan motor.
The invention makes it possible to use a punching tool for punching out carrier plates, which can then be provided for the different aforementioned use possibilities, in which in particular the tap is subsequently used as a function of different needs and is fixed at different points, so that it can act on the desired one of several turns.
According to a preferred development of the invention two feet which are bent towards one another pass through two parallel slots, so that the tap is securely held on the carrying part. The slots are regularly parallel to the heater axis in the case of heaters with a substantially cylindrical outer contour. The same orientation can be chosen for heaters with a conical contour. In this case, a connecting portion of the tap from the foot and fixing area thereof on the carrying part to the tap area to be pressed with the heating conductor, said area generally being constructed with an open, U-shaped tap sleeve, is so chosen that it can cover the maximum spacing between carrying part and heating conductor. If a displacement is necessary in areas where, due to the conical contour, the heating conductor comes close to the carrying part, the connecting portion can be given a bend, so that its total height is reduced and adapted. Alternatively, for a heating conductor guide with a conical contour, the slots run in such a way that the perpendicular line from the slots to the heating conductor is substantially identical along the slots.
Whereas taps have at least been in two parts to the extent that lugs belonging thereto were needed for fixing to the carrying part, according to the invention the tap is constructed entirely in one piece manner.